Snapchat and instagram no sound on videos

Hi, my microphone is working, my speaker is working. Volumes on full and it’s not on silent. I’ve updated the apps, uninstalled them and reinstalled them, updated the phone. Basically done everything I can but still when a do a video on Snapchat or instagram there’s just a muffled sound on play back. If I use a different device with my log in details the sound works fine. Any ideas? Thanks.